The present invention relates to a flexible cable suitably used as a jacket pipe for a gas conduit, or a liquid conduit, a covering pipe for a signal transmission line or an energy (power) transmission line and the like.
For example, a gas conduit made of rubber can be bent at an optional radius of curvature depending upon the materials used and the ratio of the inside diameter thereof to an outside diameter thereof because it is flexible. However, the passage of gas through the gas conduit is disturbed if the radius of curvature is small, for the cross section of the gas conduit is changed from oval-shaped to flat. For this reason, a gas conduit of rubber should be bent at a radius of curvature of such an extent that the passage of gas through the gas conduit cannot be disturbed. Such a desired radius of curvature of bending has not been objectively determined but has been determined on the basis of the experiences and the sixth sense of user. Accordingly, there have frequently been accidental gas leaks and the like when a gas conduit made of rubber is bent at a radius of curvature smaller than the above described desired radius of curvature. Similar problems have occurred with flexible liquid conduit and the like.